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Number of n X n symmetric 0..1 arrays with each element equal to at least two horizontal or vertical neighbors and with new values 0..1 introduced in lower triangular row major order
1

%I #7 Dec 18 2015 18:17:41

%S 0,1,1,5,24,184,2052,34481,852317,31436448,1719054683,139749375352,

%T 16887682211105,3032513808121101,809442991768500676,

%U 321179427812462958357,189437827654558885755438

%N Number of n X n symmetric 0..1 arrays with each element equal to at least two horizontal or vertical neighbors and with new values 0..1 introduced in lower triangular row major order

%H R. H. Hardin, <a href="/A192995/b192995.txt">Table of n, a(n) for n = 1..19</a>

%e Some solutions for 8X8 containing a 1

%e ..0..0..0..0..0..0..0..0....0..0..0..0..1..1..0..0....0..0..0..0..0..0..0..0

%e ..0..0..1..1..0..0..0..0....0..1..1..0..1..1..0..0....0..1..1..1..1..1..0..0

%e ..0..1..1..1..0..0..1..1....0..1..1..0..1..1..1..0....0..1..1..1..1..1..0..0

%e ..0..1..1..1..1..0..1..1....0..0..0..0..0..1..1..0....0..1..1..1..0..0..0..0

%e ..0..0..0..1..1..0..1..1....1..1..1..0..0..1..1..0....0..1..1..0..0..1..1..0

%e ..0..0..0..0..0..0..0..1....1..1..1..1..1..1..0..0....0..1..1..0..1..1..1..0

%e ..0..0..1..1..1..0..0..1....0..0..1..1..1..0..0..0....0..0..0..0..1..1..1..0

%e ..0..0..1..1..1..1..1..1....0..0..0..0..0..0..0..0....0..0..0..0..0..0..0..0

%K nonn

%O 1,4

%A _R. H. Hardin_ Jul 14 2011